While moving our 160 liter LN dewar from the 4th floor to the second floor of our building the dewar got knocked over—don’t ask how. One of our interns pulled a Hercules and righted the many-hundred pound monster single handedly. Seconds later, the dewar vented with a thundering ka-boom, blowing the cap off the top, and punching out a ceiling tile. The hallway filled with nitrogen. We were okay because we followed the rules. Everyone cleared the area. I opened the window and monitored oxygen levels on our oxygen meter. We put the dewar in the elevator without anyone in it (that is one of our standard safety rules),and took it down and outside where we chained it up.

Close-up of dewar top

The ceiling

Imagine if we didn’t have the “no people riding in the elevator with the dewar” rule. If the dewar had vented 20 seconds later and it was in an elevator with people, they most likely would have been asphyxiated. Some of the safety rules we follow with liquid nitrogen seem to guard against far-fetched scenarios that will never happen.

Looks like they can happen. Stay safe.

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14 Comments so far ↓

Hi Andy,
I think it was thermal shock from the LN splashing on the top of the dewar or some fault caused by the fall. Not sure. The only way excess pressure would have built up was if the safety was blocked somehow. How is Denver?

I’m doing well. 2 1/2 months ago I got laid off, but I just got hired on Friday to run a small recreational cooking school in Denver . Looking forward to the new challenge. Maybe I can sneak a dewar into the new place.
Your blog has become part of my weekly reading.
Love what you are doing and learning a lot from it.
Thanks.

Many of the materials used in the LN plumbing become quite brittle at cryogenic temperatures and can fracture unexpectedly.

The dewars that I used to use in my lab came from an unlikely source – livestock supply house. The standard there is a 25 liter dewar that is used for bull semen. There is an apparatus that they submerge in the LN that contains small straws of the semen. This apparatus just lifts out and what remains it a perfectly good dewar. I found that this was by far, the least expensive source for the dewar flasks.

Really good stuff you have in your site, Can i get any information on sous vide, recipes etc, spherification etc. new cooking techniques? I am a chef lecturer in england, it’s very difficult to get any recipes or people who are using the sort of stuff you use. As we progress through our careers it’s important we keep up to date so we can pass our knowledge onto others. any dvd’s videos I can access i would be most grateful. Web sites etc
Keep up the good work
John Fahy
Chef Lecturer
England

I heard of a story a couple years ago where an undergrad in the UC Berkeley physics department, who was pushing around an LN2 storage dewar in a cart, found that the elevator was broken. So, he decided to take it down the stairs.

I don’t think the dewar blew up, but it certainly put a big hole in the wall when he lost control of it.